1. Field of the Invention
This invention relates to a method and apparatus for repairing the refractory lining of a refractory vessel and, more particularly, to gunning apparatus maneuverable in large and irregularly shaped refractory vessels for positioning a nozzle assembly closely adjacent to the refractory lining at all locations within the refractory vessel, particularly those locations which are conventionally difficult to spray.
2. Description of the Prior Art
The refractory vessels used in the iron and steel industry for making, carrying, holding and pouring of molten metal, such as blast furnaces, metallurgical ladles, soaking pits, cupolas and the like are exposed to evaluated temperatures over a long period of time of use. This results in deterioration of the interior refractory surface. Consequently, the surface must be either periodically replaced or repaired.
The interior surface of a refractory vessel is repaired first by removing as much of the scale and loose debris from the surface of the vessel before the vessel is relined so that the material spray will securely adhere to the interior surface. Conventional, pressurized air and water are utilized to remove the scale from the wall of the vessel and prepare it for spray relining.
U.S. Pat. Nos. 1,928,621; 3,902,670 and 4,181,258 are examples of well known apparatus for cleaning the surface of refractory vessels. A high pressure spray from a rotatable nozzle utilizes a variety of materials for dislodging loose material from the surface of the vessel. A combination of a stream of water, air, sand or other operating medium are utilized. The medium is directed over the interior surface of the vessel to dislodge the loose material and thereafter air may be blown over the surface to dry it in preparation for the refractory relining operation.
Conventionally, the refractory relining operation requires equipment separate from the equipment used to clean the interior walls of the vessel. Consequentially, the cleaning equipment and the means for mounting it in the vessel must be removed and the refractory spray equipment installed in its place. Cleaning and repairing the vessel for relining followed by relining the vessel are very cumbersome and time consuming operations. One set of equipment must be installed and thereafter removed to permit the installation of another set of equipment.
The conventionally known gunning apparatus for relining a refractory vessel includes a spray unit, such as a nozzle assembly, that is supported for rectilinear and rotational movement within the vessel. The unit is typically supported on a movable carriage either on an overhead gantry or beam within or above the vessel or on a transport car movable on rails or ground below the vessel. Exemplary gunite devices supported overhead and lowered into the vessel, such as a blast furnace or ladle, are disclosed in U.S. Pat. Nos. 3,797,745; 3,799,445; 4,099,708; 4,163,546; 4,167,246; 4,211,367; 4,421,275; 4,860,422; and 5,178,329. Each of these devices includes a rotatable nozzle where the dry refractory and water are mixed at or adjacent to the nozzle outlet for spraying onto the refractory surface.
To accommodate the transport of dry refractory and water to the nozzle outlet, a swivel mechanism is required for the rotatable connection of either a water line or the refractory line to the rotatable nozzle. The separate delivery of the dry refractory and water to the nozzle requires a complex arrangement for supporting and moving the nozzle assembly both vertically and rotatably. Consequentially, for irregularly configured vessels such as a blast furnace, where the interior diameter of the vessel varies along the length from top to bottom, it is difficult to closely position the nozzle relative to the surface. The nozzle must be positioned a distance from the wall so that when the refractory material is sprayed it adheres and is not deflected from the surface.
In other applications, the refractory material and water is mixed from a source outside of the vessel, such as at a swivel point supported on a gantry above the vessel. Examples of this type of arrangement for mixing the refractory material and water delivered through a conduit into the vessel where the conduit is supported for rectilinear and rotational movement relative to the interior wall are disclosed in U.S. Pat. Nos. 3,351,289; 4,301,998; 4,337,897; and 4,494,737.
It is also known to support a gunite device on a transport car movable on rails or on a mobile vehicle positioned below the refractory vessel. The spray nozzle is moved vertically, downwardly or upwardly, to a desired position oppositely the vessel wall. The nozzle is then rotated to apply the mixed refractory and water onto the surface. Examples of this arrangement are disclosed in U.S. Pat. Nos. 3,957,203; 4,085,894; 4,779,798.
One limitation of known gunite devices is the inability to position the spray nozzle at difficult positions to reach within the vessel. This is encountered in vessels having irregular shapes, such as blast furnaces and ladles where the interior circumference and diameter of the vessel varies along the length and depth of the vessel. In order to overcome these problems, gunite devices have been developed for remote control of a spray nozzle for positioning at desired locations within the vessel. Devices of this type are disclosed in U.S. Pat. Nos. 3,973,730; 4,251,063; 4,690,327 and 5,158,614.
While some prior art devices are effective for relining irregularly shaped vessels, they require complex support apparatus that is limited to vessels of a particular configuration. In other words, the gunite device can not be used at one sight for repairing a blast furnace and then transported to another sight for repairing a ladle or the like without making substantial modifications to the support apparatus.
Therefore, there is need for gunite apparatus that is universally adaptable to apply refractory material to the interior surface of a vessel at any point within the vessel regardless the interior configuration of the vessel. The unit must be efficiently moved into and out of position without requiring support mechanisms that must be erected specifically for the interior configuration of the vessel. The spray nozzle must compactly transported to the sight and moved into position for custom spraying. It would also be beneficial if the gunite apparatus could be used to remove scale and loose debris from the vessel wall prior to relining.